html, body {
    height: 100%;
    margin: 0;
    overflow: hidden;
}
body {
    display: flex;
    align-items: center;
    justify-content: center;
    background: #000;
}
main {
    display: flex;
}
p {
    line-height: 1;
}
span {
    display: block;
    width: 2vmax;
    height: 2vmax;
    font-size: 2vmax;
    color: #9bff9b11;
    text-align: center;
    font-family: "Helvetica Neue", Helvetica, sans-serif;
}